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Research Notes

Lighting the way to real-time fecal contamination detection

Detecting
fecal contamination in water just became more accurate. Researchers have
developed a technology that detects in water trace amounts of urobilin, a
byproduct excreted in urine and feces of many mammals such as humans and
livestock.

Traditional detection methods are limited by high costs, small sample
sizes, and lengthy analysis times. But this technology finds indicators of
fecal contamination thousandths- and even millionths-of-times smaller than
those found by conventional methods. It also can be produced for a few hundred
dollars, and is capable of analyzing large samples in real-time, according to a
Texas A&M University (College Station) news release.

When
mixed with zinc ions, urobilin forms a phosphorescent compound and gives off a
greenish glow when examined under ultraviolet light. But samples with low
concentrations only give off a weak glow, making it difficult to analyze the
sample.

Vladislav
Yakovlev, professor in Texas A&M University’s Department of Biomedical
Engineering, worked with a team to thoroughly excite extremely small amounts of
urobilin in large samples of water. The researchers collected the resulting
phosphorescent emission with the help of a device they referred to as an
“integrated cavity,” the news release says.

The
integrated cavity is a hollow cylindrical container manufactured in Yakovlev’s
laboratory. A water sample is placed inside the cylinder where it interacts
with zinc ions. A laser light is used to excite the urobilin compound in the
sample, causing even low levels of urobilin to glow. The only way light exits
the cylinder is through the hole it entered by, allowing researchers to
efficiently collect the resulting phosphorescent emission and direct it to a
photo detector such as a spectrometer for analysis, Yakovlev explained in the
release.

Using the
integrated cavity, the team of researchers detected the presence of urobilin
down to a nanomole per liter. And because the system is capable of sampling a
larger water sample, it promises a more accurate analysis of a system’s overall
water quality, Yakovlev said in the release.

Yakovlev
and the team are working to commercialize the technology. The research is
featured in the journal Proceedings of the National Academy of Sciences.

Carbon nanomaterials will travel

As use of
graphene and other carbon-based nanomaterials in electronics increases, their
potential to affect the health of humans and the environment also increases.
So, University of California–Riverside Bourns College of Engineering
researchers examined the stability of graphene oxide and its movement in both
surface and groundwater.

The
researchers found that graphene oxide nanoparticles are very mobile in lakes or
streams and are likely to harm the environment, according to a university news
release.

The
nanoparticles’ behavior differed significantly in groundwater versus surface
water. Because of groundwater’s higher degree of hardness and lower
concentration of natural organic matter, graphene oxide nanoparticles tended to
become less stable and eventually settle out or be removed in subsurface
environments. In surface waters where there is more organic material and less
hardness, nanoparticles remained stable and moved farther, especially in
subsurface layers of the waterbodies, the news release says.

The
research article, “Stability and Transport of Graphene Oxide Nanoparticles in
Groundwater and Surface Water,” was published in the journal Environmental
Engineering Science.

Researchers examine foam management in nutrient removal facilities

The classifying selector, a method for foam elimination introduced in
2001, has been confused with other technologies and practices. Brown and
Caldwell (Walnut Creek, Calif.) researchers decided to examine the various
methods for foam management or elimination in activated sludge facilities. The
research article providing this review appears in the June issue of Water
Environment Research.

High
residence times and trapping by baffles cause nuisance foam-causing organisms
to accumulate in facilities. This occasionally causes effluent with high levels
of total suspended solids and leads to digester foaming when wasted.

The
classifying selector, based on sound biological and physical principles, needs
no chemicals and minimal operator attention to work. When properly applied, it
will prevent nuisance foams in biological nutrient removal facilities. It can
be distinguished from other surface foam wasting schemes by maintaining negative
selection pressure so nuisance foam-causing organisms are unable to gain a
foothold in sufficient numbers. The process uses the propensity of
nuisance-causing organisms to attach to bubbles and establish a rising velocity
to enrich them in a surface mixed liquor layer, where they are wasted, the
article says. However, publications have not adequately described the process,
so benefits of foam elimination from classifying sector concepts have not been
widely obtained.

For inherent foam trapping situations, the only solution is surface foam
wasting because foam can’t be eliminated. The article addresses potential
efficiency gains possible in these situations.

The
authors note that strategies to manage or eliminate foam rely on the designer
and facility owner to choose a nutrient removal process and implement its
features. They also suggest developing designs with the operator in mind since
the type of wasting conducted relies on the operator as he or she works to
optimize facility operation. The article, “A Critical Review of Nuisance Foam
Formation and Biological Methods for Foam Management or Elimination in Nutrient
Removal Facilities,” can be downloaded free at http://goo.gl/ACSTtf.

Water
Environment Research offers open access to one article per issue on a range
of important technical topics such as nutrient removal, stormwater, and
biosolids recycling.